Effect of Boundary Conditions on Nonlinear Vibrations of Circular Cylindrical Panels

Geometrically nonlinear vibrations of circular cylindrical panels with different boundary conditions and subjected to harmonic excitation are numerically investigated. The Donnell’s nonlinear strain–displacement relationships are used to describe geometric nonlinearity; in-plane inertia is taken into account. Different boundary conditions are studied and the results are compared; for all of them zero normal displacements at the edges are assumed. In particular, three models are considered in order to investigate the effect of different boundary conditions: Model A for free in-plane displacement orthogonal to the edges, elastic distributed springs tangential to the edges and free rotation; Model B for classical simply supported edges; and Model C for fixed edges and distributed rotational springs at the edges. Clamped edges are obtained with Model C for the very high value of the stiffness of rotational springs. The nonlinear equations of motion are obtained by the Lagrange multimode approach, and are studied by using the code AUTO based on the pseudo-arclength continuation method. Convergence of the solution with the number of generalized coordinates is numerically verified. Complex nonlinear dynamics is also investigated by using bifurcation diagrams from direct time integration and calculation of the Lyapunov exponents and the Lyapunov dimension. Interesting phenomena such as (i) subharmonic response; (ii) period doubling bifurcations; (iii) chaotic behavior; and (iv) hyper-chaos with four positive Lyapunov exponents have been observed.